initial exercise files (minus README content)

README.md

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+# Bitcoin Whitepaper Exercises
+
+In these exercises, you will learn about blockchains from the perspective of the [original Bitcoin Whitepaper](https://bitcoin.org/en/bitcoin-paper).
+
+* [Hashing](hashing/README.md)
+* [Transactions](transactions/README.md)
+* [Wallet](wallet/README.md)
+* [Proof of Work](pow/README.md)
+* [Incentives](incentives/README.md)

hashing/README.md

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+# Bitcoin Whitepaper Exercises - Hashing
+
+TODO

hashing/hashing.js

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+"use strict";
+
+var crypto = require("crypto");
+
+// The Power of a Smile
+// by Tupac Shakur
+var poem = [
+	"The power of a gun can kill",
+	"and the power of fire can burn",
+	"the power of wind can chill",
+	"and the power of a mind can learn",
+	"the power of anger can rage",
+	"inside until it tears u apart",
+	"but the power of a smile",
+	"especially yours can heal a frozen heart",
+];
+
+var Blockchain = {
+	blocks: [],
+};
+
+// Genesis block
+Blockchain.blocks.push({
+	index: 0,
+	hash: "000000",
+	data: "",
+	timestamp: Date.now(),
+});
+
+// TODO: insert each line into blockchain
+// for (let line of poem) {
+// }
+
+// console.log(`Blockchain is valid: ${verifyChain(Blockchain)}`);
+
+
+// **********************************
+
+function blockHash(bl) {
+	return crypto.createHash("sha256").update(
+		// TODO: use block data to calculate hash
+	).digest("hex");
+}

incentives/README.md

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+# Bitcoin Whitepaper Exercises - Incentives
+
+TODO

incentives/generate-keys.js

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+"use strict";
+
+var path = require("path");
+var fs = require("fs");
+var openpgp = require("openpgp");
+
+const KEYS_DIR = path.join(__dirname,"keys");
+
+var options = {
+	userIds: [{ name: "Bitcoin Whitepaper", email: "[email protected]" }],
+	numBits: 2048,
+	passphrase: "",
+};
+
+openpgp.generateKey(options).then(function onGenerated(key) {
+	try { fs.mkdirSync(KEYS_DIR); } catch (err) {}
+
+	fs.writeFileSync(path.join(KEYS_DIR,"priv.pgp.key"),key.privateKeyArmored,"utf8");
+	fs.writeFileSync(path.join(KEYS_DIR,"pub.pgp.key"),key.publicKeyArmored,"utf8");
+
+	console.log("Keypair generated.");
+});

incentives/incentives.js

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+"use strict";
+
+var path = require("path");
+var fs = require("fs");
+var crypto = require("crypto");
+
+const KEYS_DIR = path.join(__dirname,"keys");
+const PUB_KEY_TEXT = fs.readFileSync(path.join(KEYS_DIR,"pub.pgp.key"),"utf8");
+
+// The Power of a Smile
+// by Tupac Shakur
+var poem = [
+	"The power of a gun can kill",
+	"and the power of fire can burn",
+	"the power of wind can chill",
+	"and the power of a mind can learn",
+	"the power of anger can rage",
+	"inside until it tears u apart",
+	"but the power of a smile",
+	"especially yours can heal a frozen heart",
+];
+
+const maxBlockSize = 4;
+const blockFee = 5;
+var difficulty = 16;
+
+var Blockchain = {
+	blocks: [],
+};
+
+// Genesis block
+Blockchain.blocks.push({
+	index: 0,
+	hash: "000000",
+	data: "",
+	timestamp: Date.now(),
+});
+
+var transactionPool = [];
+
+addPoem();
+processPool();
+countMyEarnings();
+
+
+// **********************************
+
+function addPoem() {
+	// TODO: add lines of poem as transactions to the transaction-pool
+}
+
+function processPool() {
+	// TODO: process the transaction-pool in order of highest fees
+}
+
+function countMyEarnings() {
+	// TODO: count up block-fees and transaction-fees
+}
+
+function createBlock(data) {
+	var bl = {
+		index: Blockchain.blocks.length,
+		prevHash: Blockchain.blocks[Blockchain.blocks.length-1].hash,
+		data,
+		timestamp: Date.now(),
+	};
+
+	bl.hash = blockHash(bl);
+
+	return bl;
+}
+
+function blockHash(bl) {
+	while (true) {
+		bl.nonce = Math.trunc(Math.random() * 1E7);
+		let hash = crypto.createHash("sha256").update(
+			`${bl.index};${bl.prevHash};${JSON.stringify(bl.data)};${bl.timestamp};${bl.nonce}`
+		).digest("hex");
+
+		if (hashIsLowEnough(hash)) {
+			return hash;
+		}
+	}
+}
+
+function hashIsLowEnough(hash) {
+	var neededChars = Math.ceil(difficulty / 4);
+	var threshold = Number(`0b${"".padStart(neededChars * 4,"1111".padStart(4 + difficulty,"0"))}`);
+	var prefix = Number(`0x${hash.substr(0,neededChars)}`);
+	return prefix <= threshold;
+}
+
+function createTransaction(data) {
+	var tr = {
+		data,
+	};
+
+	tr.hash = transactionHash(tr);
+
+	return tr;
+}
+
+function transactionHash(tr) {
+	return crypto.createHash("sha256").update(
+		`${JSON.stringify(tr.data)}`
+	).digest("hex");
+}

pow/README.md

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+# Bitcoin Whitepaper Exercises - Proof of Work
+
+TODO

pow/pow.js

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+"use strict";
+
+var crypto = require("crypto");
+
+// The Power of a Smile
+// by Tupac Shakur
+var poem = [
+	"The power of a gun can kill",
+	"and the power of fire can burn",
+	"the power of wind can chill",
+	"and the power of a mind can learn",
+	"the power of anger can rage",
+	"inside until it tears u apart",
+	"but the power of a smile",
+	"especially yours can heal a frozen heart",
+];
+
+var difficulty = 10;
+
+var Blockchain = {
+	blocks: [],
+};
+
+// Genesis block
+Blockchain.blocks.push({
+	index: 0,
+	hash: "000000",
+	data: "",
+	timestamp: Date.now(),
+});
+
+for (let line of poem) {
+	let bl = createBlock(line);
+	Blockchain.blocks.push(bl);
+	console.log(`Hash (Difficulty: ${difficulty}): ${bl.hash}`);
+
+	difficulty++;
+}
+
+
+// **********************************
+
+function createBlock(data) {
+	var bl = {
+		index: Blockchain.blocks.length,
+		prevHash: Blockchain.blocks[Blockchain.blocks.length-1].hash,
+		data,
+		timestamp: Date.now(),
+	};
+
+	bl.hash = blockHash(bl);
+
+	return bl;
+}
+
+function blockHash(bl) {
+	// TODO
+}
+
+function hashIsLowEnough(hash) {
+	// TODO
+}
+
+function verifyBlock(bl) {
+	if (bl.data == null) return false;
+	if (bl.index === 0) {
+		if (bl.hash !== "000000") return false;
+	}
+	else {
+		if (!bl.prevHash) return false;
+		if (!(
+			typeof bl.index === "number" &&
+			Number.isInteger(bl.index) &&
+			bl.index > 0
+		)) {
+			return false;
+		}
+		if (bl.hash !== blockHash(bl)) return false;
+	}
+
+	return true;
+}
+
+function verifyChain(chain) {
+	var prevHash;
+	for (let bl of chain.blocks) {
+		if (prevHash && bl.prevHash !== prevHash) return false;
+		if (!verifyBlock(bl)) return false;
+		prevHash = bl.hash;
+	}
+
+	return true;
+}

transactions/README.md

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+# Bitcoin Whitepaper Exercises - Transactions
+
+TODO

transactions/generate-keys.js

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+"use strict";
+
+var path = require("path");
+var fs = require("fs");
+var openpgp = require("openpgp");
+
+const KEYS_DIR = path.join(__dirname,"keys");
+
+var options = {
+	userIds: [{ name: "Bitcoin Whitepaper", email: "[email protected]" }],
+	numBits: 2048,
+	passphrase: "",
+};
+
+openpgp.generateKey(options).then(function onGenerated(key) {
+	try { fs.mkdirSync(KEYS_DIR); } catch (err) {}
+
+	fs.writeFileSync(path.join(KEYS_DIR,"priv.pgp.key"),key.privateKeyArmored,"utf8");
+	fs.writeFileSync(path.join(KEYS_DIR,"pub.pgp.key"),key.publicKeyArmored,"utf8");
+
+	console.log("Keypair generated.");
+});

transactions/package.json

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+{
+	"name": "solutions-transactions",
+	"main": "transactions.js",
+	"dependencies": {
+		"openpgp": "~3.0.7"
+	}
+}